U.S. patent application number 10/441045 was filed with the patent office on 2003-11-27 for audio control device.
This patent application is currently assigned to Realtek Semiconductor Corp.. Invention is credited to Chang, Yi-Shu, Huang, Jui-Cheng, Su, Chu-Ting, Wang, Wen-Chi.
Application Number | 20030219134 10/441045 |
Document ID | / |
Family ID | 29547017 |
Filed Date | 2003-11-27 |
United States Patent
Application |
20030219134 |
Kind Code |
A1 |
Su, Chu-Ting ; et
al. |
November 27, 2003 |
Audio control device
Abstract
An Audio Codec which comprises a power selecting circuit an
audio compiler circuit and a control amplifier circuit The power
selecting circuit receives at least a primary power source and an
auxiliary power source and outputs a working power selected from
the power sources. The auxiliary power source is selected and
output to the control amplifier circuit only when the computer is
at a power-off status. When the computer is power-on, the primary
power source will be selected and output to both the audio compiler
circuit and the control amplifier circuit. Therefore, the Audio
Codec of the present invention only needs one set of internally
furnished control amplifier circuit to both operate on the normal
power-on status and perform the Power OFF CD function.
Inventors: |
Su, Chu-Ting; (Hsinchu,
TW) ; Chang, Yi-Shu; (Tainan, TW) ; Huang,
Jui-Cheng; (Hsinchu, TW) ; Wang, Wen-Chi;
(YunLi Hsien, TW) |
Correspondence
Address: |
BRUCE H. TROXELL
SUITE 1404
5205 LEESBURG PIKE
FALLS CHURCH
VA
22041
US
|
Assignee: |
Realtek Semiconductor Corp.
|
Family ID: |
29547017 |
Appl. No.: |
10/441045 |
Filed: |
May 20, 2003 |
Current U.S.
Class: |
381/104 ; 307/80;
704/500 |
Current CPC
Class: |
H03F 3/68 20130101 |
Class at
Publication: |
381/104 ; 307/80;
704/500 |
International
Class: |
H02J 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 21, 2002 |
TW |
91110583 |
Claims
What is claimed is:
1. An Audio Codec integrated circuit, comprising: an audio compiler
circuit for performing analog/digital signal transformations; a
control amplifier circuit for accepting an input audio signal and
outputs an amplified output signal; and a power selecting circuit
connecting to both the audio compiler circuit and the control
amplifier circuit, said power selecting circuit being capable of
receiving at least a primary power source and an auxiliary power
source and outputting one of the power sources according to a
selecting signal; wherein said power selecting circuit outputs the
auxiliary power source to said control amplifier circuit when there
is only the auxiliary power source being supplied thereto; wherein
said power selecting circuit outputs the primary power source to
both the audio compiler circuit and the control amplifier circuit
when there is the primary power source being supplied thereto.
2. The Audio Codec integrated circuit of claim 1, wherein said
selecting signal is according to the absence of the primary power
source.
3. The Audio Codec integrated circuit of claim 1, wherein the power
selecting circuit includes a separation circuit and a switch
circuit; the separation circuit separates the primary power source
from the auxiliary power source such that only one of the power
sources will be output by the power selecting circuit; and, the
switch circuit controls the output of the auxiliary power source
according to the selecting signal in such a manner that the power
selecting circuit outputs the auxiliary power source only if there
is no primary power source being received thereby.
4. The Audio Codec integrated circuit of claim 3, wherein the
selecting signal is the primary power source itself; the switch
circuit is "off" when the primary power source is at a high voltage
status, and "on" when the primary power source is at a low voltage
status.
5. The Audio Codec integrated circuit of claim 3, wherein the
separation circuit comprises at least two Schottky diodes connected
to each other in parallel; one of the Schottky diode is connected
to the primary power source, while another one is connected to an
output end of the switch circuit; and, the switch circuit comprises
at least one metal-oxide-semiconductor field effect transistor
(MOSFET) having an input end thereof connected to the auxiliary
power source and a gate end thereof connected to the selecting
signal.
6. The Audio Codec integrated circuit of claim 1, wherein the input
audio signal is coming from a CD_L port a CD_R port and CD_GND port
of a CD-ROM device,
7. The Audio Codec integrated circuit of claim 1, wherein the
control amplifier circuit comprises a first amplifier circuit, a
second amplifier circuit, a third amplifier circuit, and a fourth
amplifier circuit; the first amplifier circuit is connected to the
second amplifier circuit in serial so as to process a first channel
of the input audio signal; and, the third amplifier circuit is
connected to the fourth amplifier circuit in serial so as to
process a second channel of the input audio signal.
8. The Audio Codec integrated circuit of claim 7, wherein the first
and the third amplifier circuits each has an input end thereof
connecting to a ground signal port "CD_GND" of a CD-ROM device.
9. The Audio Codec integrated circuit of claim 1, wherein the power
selecting circuit further receiving a digital power source, and
said selecting signal is according to the digital power source.
10. An audio control device, comprising: a power selecting circuit
for receiving at least a first power source and a second power
source and outputting a working power selected from said first and
second power sources; and an audio compiler/control circuit
connecting to said power selecting circuit for accepting the
working power, the audio compiler/control circuit having an audio
compiler circuit and a control amplifier circuit built therein;
wherein the audio compiler circuit performs analog/digital signal
transformations only if the working power is the first power
source; wherein said control amplifier circuit accepts an input
audio signal and outputs an amplified output signal no matter what
the working power is the first power source or the second power
source.
11. The audio control device of claim 10, wherein the power
selecting circuit includes a separation circuit and a switch
circuit; the separation circuit separates the first power source
from the second power source such that only one of the power
sources will be output by the power selecting circuit; and, the
switch circuit controls the output of the second power source in
such a manner that the power selecting circuit outputs the second
power source only if there is no first power source being received
thereby.
12. The audio control device of claim 11, wherein the separation
circuit comprises at least two Schottky diodes connected to each
other in parallel; one of the Schottky diode is connected to the
first power source, while another one is connected to an output end
of the switch circuit; and, the switch circuit comprises at least
one metal-oxide-semiconductor field effect transistor (MOSFET)
having an input end thereof connected to the second power source
and a gate end thereof connected to a selecting signal.
13. The audio control device of claim 10, wherein the input audio
signal is coming from a CD_L port, a CD_R port and CD_GND port of a
CD-ROM device.
14. The audio control device of claim 10, wherein the control
amplifier circuit comprises a first amplifier circuit, a second
amplifier circuit, a third amplifier circuit, and a fourth
amplifier circuit; the first amplifier circuit is connected to the
second amplifier circuit in serial so as to process a first channel
of the audio signal; and, the third amplifier circuit is connected
to the fourth amplifier circuit in serial so as to process a second
channel of the audio signal; wherein the first and the third
amplifier circuits each has an input end thereof connecting to a
ground signal port "CD_GND" of a CD-ROM device.
15. The audio control device of claim 10, wherein the audio
compiler/control circuit and the power selecting circuit are built
in a single IC chip.
16. An audio amplifier device of an electronic device, said
electronic device being capable of providing a first power source
and a second power source, said audio amplifier device being
operatable by using said second power source when the first power
source is absent, said audio device comprising: a first amplifier
for receiving an input audio signal and outputting a first
amplified signal; a volume control circuit for receiving said first
amplified signal and outputting a controlled volume signal; a
switch circuit connecting to both the first amplifier and the
volume control circuit for receiving signals therefrom, said switch
circuit outputting a selected signal selected from the first
amplified signal and the controlled volume signal according to a
control signal; and a second amplifier for receiving said selected
signal and outputting an output audio signal; wherein said control
signal is according to the absence of the first power source.
17. The audio amplifier device of claim 16, wherein the control
signal comprises a first control status and a second control
status; and wherein the switch circuit further comprises: a first
channel switch connecting to the first amplifier for receiving the
first amplified signal, said first channel switch outputting said
first amplified signal as the selected signal when the control
signal is at the first control status; and a second channel switch
connecting to the volume control circuit for receiving the
controlled volume signal, said first channel switch outputting said
controlled volume signal as the selected signal when the control
signal is at the second control status.
18. The audio amplifier device of claim 17 further comprising a
power selecting circuit for generating said control signal, wherein
said power selecting circuit comprises: a MOS transistor having a
gate, a source and a drain, said gate being connected to the first
power source, said source being connected to a ground, said drain
being connected to the second power source; and a node connecting
to the drain of the MOS transistor for outputting a VC signal;
wherein, said power selecting circuit outputting said VC signal as
the control signal to the first channel switch when the first power
source is absent; wherein, said power selecting circuit outputting
said first power source as the control signal to the second channel
switch when the first power source is available.
19. The audio amplifier device of claim 16, wherein the electronic
device is a computer.
20. The audio amplifier device of claim 16, wherein the audio
amplifier device is built-in an Audio Codec chip.
Description
FIELD OF THE INVENTION
[0001] The invention relates to an audio control circuit in
particular to an Audio Codec chip with a power selecting circuit
that can accept both a computer primary power supply and a computer
auxiliary power supply so as to attain the Power Off CD function,
that is, to play music from a CD-ROM device when the computer
system is power-off.
BACKGROUND OF THE INVENTION
[0002] The needs for the functions provided by personal computers
(also referred as PC hereinafter) are vastly increased, and so as
the hardware of the computers. During the recent years, Multimedia
features and applications thereof have become an important issue,
and an audio system with high performance and high quality also
becomes a necessity of the computer.
[0003] During an ordinary operation mode of the computer, the data
processed by the computer is Digital, however the voice we heard is
Analog. Therefore, in the audio system of the computer, it needs to
convert Digital signals to Analog signals, and also needs to
convert Analog signals to Digital signals. The device that manages
such a work in the audio system is so-called "Audio Codec".
Therefore, INTEL Corp. has defined a set of standards for audio
systems, namely the "Audio Codec'97". This design not only can
prevent the analog signals from being interfered by the digital
signals, but also can improve the Signal-to-Noise Ratio (SNR) (p.s.
the SNR of PC in market can now reach 90 db). As a result, "Audio
Codec" has become a mainstream in the audio system of the personal
computers.
[0004] On the other hand, there has been established with a set of
standards of PC Power Management in the operating system of PC. The
PC Power Management has a special feature to allow the computer to
be "Wake-Up" by its auxiliary power source even when the computer
is at a power-off status. It is found that, the auxiliary power
source not only can be used to provide the "Wake-Up" function of
PC, but also can be applied on various multimedia applications.
Hence, some computer manufacturers developed a function, so-called
"Power Off CD", which can play music CD by using the aforesaid
auxiliary power source of the PC Power Management system even when
the computer is "power-off". That is, to provide an auxiliary power
source to the CD-ROM device so as to allow the users to play music
CD with the CD-ROM device without the need to power-on the
computer.
[0005] However, since the conventional standards of the "Audio
Codec'97" are merely for audio applications only, therefore, we
will need to apply additional power amplifiers and switches (which
are furnished outside the "Audio Codec'97") to connect with both of
the CD-ROM device and the auxiliary power source so as to perform
the "Power Off CD" function.
[0006] Please refer to FIG. 1, it is an audio device of prior art
which uses external power amplifies and external switches to
co-operate with the Audio Codec chip for attaining the function of
"Power Off CD" (i.e., to play CD music when the primary power
source of PC is "power-off"). As shown in FIG. 1, the audio device
1 includes an Audio Codec 3 and an audio control circuit 2. The
Audio Codec 3 is a single IC chip 30 (also referred as Audio Codec
chip 30 hereinafter) which is preferably an "Audio Codec'97" chip
The audio control circuit 2 comprises two switch circuits 23, 24, a
voltage divider circuit 25, and two amplifier circuits 21, 22. The
two amplifier circuits include the first amplifier circuit 21 and
the second amplifier circuit 22. Audio signals coming from the Left
Channel (CD_L) of the CD-ROM device are amplified by the first
amplifier circuit 21. And then, the amplified audio signals are
transmitted through the first switch circuit 23 (PWOFFCD_L) which
controls whether the signals will be output to (or played by) the
left speaker 26 or not. Similarly, audio signals coming from the
Right Channel (CD_R) of a CD-ROM device are amplified by the second
amplifier circuit 22. These amplified audio signals are then
transmitted through the second switch circuit 24 (PWOFFCD_R) which
controls whether these signals will be output to (or played by) the
right speaker 27 or not The Left Channel (CD_L), Right Channel
(CD_R) and Ground (CD_GND) of the CD-ROM device are also connected
to corresponding input pins of the Audio Codec chip 30. Output
pins, including Out_L and Out_R, of the Audio Codec chip 30 are
also connected to corresponding speakers 26, 27 respectively.
[0007] In addition, there are several power supply pins such as 3.3
Vdigital, 5 Vaux, and 5 VAudio. Wherein, 5 VAudio is for driving
the Audio Codec chip 30 and the amplifier circuits 21, 22. 3.3
Vdigital is used as a control signal for digital control logic of
the Audio Codec chip 30. Both 5 VAudio and 3.3 Vdigital are primary
power sources of the and are available only when the PC is
power-on. 5 Vaux is the auxiliary power source and are available
even when the PC is power-off. It can be seen from FIG. 1 that, in
a prior art audio device 1, the Audio Codec chip 30 can only accept
the primary power sources 5 VAudio and 3.3 Vdigital. Therefore, the
Audio Codec chip 30 can only work in a PC power-on status. In order
to achieve the goal of "Power Off CD", the prior art audio device 1
needs to apply additional and external amplifier circuits 21, 22
which are driven by the auxiliary power source 5 Vaux. When the PC
is power-off, the auxiliary power source 5 Vaux is still available
such that the audio signals coming from the CD-ROM device can be
amplified by ink amplifier circuits 21, 22 and then output to the
speakers 26, 27. It is noted that, the audio control circuit 2
provides no power selecting function at all. Which means, the Audio
Codec chip 30 can only accept the primary power sources 5 VAudio
and 3.3 Vdigital, while the external amplifier circuits 21, 22 can
only accept the auxiliary power source 5 Vaux. The 3.3 Vdigital and
5 Vstandby used in the audio control circuit 2 are merely control
signals for controlling the switches 23, 24 only but not to provide
"power selecting.infin. function.
[0008] However, it is understood that the Audio Codec chip 30
itself is also furnished (built-in) with internal amplifier
circuits (not shown in the figures). These internal amplifier
circuits provide not function when the PC is power-off since no
power is supplied thereto. It is obvious that, the installment of
the extol amplifier circuits 21, 22 addition to the internal ones
is a waste of money, but also a waste of space on the circuit
board. Moreover, the prior art audio control circuit 2 shown in
FIG. 1 can only provides the function of Power OFF CD but cannot
prevent Noise which is generated when operating the CD-ROM
device.
SUMMARY OF THE INVENTION
[0009] To solve the foregoing problems of the prior art, the
primary object of the present invention is to provide an audio
control device which uses only one set of amplifier circuits to
operate in both PC power-on and PC power-off statuses. As a result,
the number of components, cost and space needed for the circuits
are reduced.
[0010] Another object of the present invention is to provide an
audio control device which comprises a power selecting circuit for
outputting a power selected from a primary power source and an
auxiliary power source. The selected power is then output to the
internal amplifier circuits which are built-in the Audio Code chip.
Therefore, no matter the PC is power-on or power-off, the internal
amplifier circuits of Audio Code chip can always be driven by the
selected power output from the power selecting circuit.
[0011] A further object of the present invention is to provide an
audio control device, wherein the aforesaid power selecting circuit
is built-in (integrated-in) the Audio Code chip to be a single IC
chip.
[0012] Yet another object of the present invention is to provide an
audio control device in which a ground signal of the CD-ROM device
is connected to an input pin of the amplifier circuit for reducing
the Noise generated by the CD-ROM device so as to obtain a better
effect of audio output.
[0013] In order to achieve the aforesaid objects, a preferred
embodiment of the audio control device in accordance with the
present invention comprises:
[0014] an audio compiler circuit for performing analog/digital
signal transformations of audio signals;
[0015] a control amplifier circuit for accepting an input audio
signal and outputting an amplified output signal; and
[0016] a power selecting circuit connecting to both the audio
compiler circuit and the control amplifier circuit, said power
selecting circuit receiving at least a first power source and a
second power source and outputting one of the power sources
according to a selecting signal;
[0017] wherein the audio compiler circuit and the control amplifier
circuit are integrated into a single IC chip (namely the Audio
Codec chip);
[0018] wherein said power selecting circuit outputs the second
power source to said audio compiler circuit when there is only the
second power source being supplied thereto;
[0019] wherein said power selecting circuit outputs the first power
source to both the audio compiler circuit and the control amplifier
circuit when there is the first power source being supplied
thereto.
[0020] Preferably, the control amplifier circuit comprises a first
amplifier circuit, a second amplifier circuit, a third amplifier
circuit, and a fourth amplifier circuit. The first amplifier
circuit is connected to the second amplifier circuit in serial so
as to process a first channel of the input audio signal. The third
amplifier circuit is connected to the fourth amplifier circuit in
serial so as to process a second channel of the input audio signal.
Wherein, the first and the third amplifier circuits each has an
input end thereof connecting to a ground signal port "CD_GND" of a
CD-ROM device.
[0021] Preferably, the power selecting circuit, the audio compiler
circuit and the control amplifier circuit are all integrated into a
single IC chip.
[0022] Yet another object of the present invention is to provide an
audio amplifier device of an electronic device. The electronic
device is capable of providing a first power source and a second
power source. The audio amplifier device is operatable by using
said second power source when the first power source is absent. The
audio device comprises:
[0023] a first amplifier for receiving an input audio signal and
outputting a first amplified signal;
[0024] a volume control circuit for receiving said first amplified
signal and outputting a controlled volume signal;
[0025] a switch circuit connecting to both the first amplifier and
the volume control circuit for receiving signals therefrom, the
switch circuit outputting a selected signal selected from the first
amplified signal and the controlled volume signal according to a
control signal; and
[0026] a second amplifier for receiving said selected signal and
outputting an output audio signal;
[0027] wherein said control signal is according to the absence of
the first power source.
[0028] Other and further features, advantages and benefits of the
invention will become apparent in the following description taken
in conjunction with the following drawings. It is to be understood
that the foregoing general description and following detailed
description are exemplary and explanatory but are not to be
restrictive of the invention. The accompanying drawings are
incorporated in and constitute a part of this application and,
together with the description, serve to explain the principles of
the invention in general terms. Like numerals refer to like parts
throughout the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The objects, spirits and advantages of the preferred
embodiments of the present invention will be readily understood by
the accompanying drawings and detailed descriptions, wherein:
[0030] FIG. 1 is a schematic diagram showing an audio control
circuit of prior art.
[0031] FIG. 2 is a schematic diagram illustrating the first
embodiment of the audio control device in accordance with the
present invention.
[0032] FIG. 3 is a schematic diagram illustrating the second
embodiment of the audio control device in accordance with the
present invention.
[0033] FIG. 4 is a schematic diagram showing a status table of
power selection performed by the power selecting circuit 7 of FIG.
3.
[0034] FIG. 5 is a schematic diagram showing the power selecting
circuit being applied to an amplifier of the internal amplifier
circuit of the present invention so as to obtain the same status
table as which illustrated in FIG. 4.
[0035] FIG. 6 is a schematic diagram showing a more detail of the
internal amplifier circuit in accordance with the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0036] The present invention discloses an audio control device with
specially designed power selecting circuit, which can be
exemplified by the preferred embodiments as described
hereinafter.
[0037] Please refer to FIG. 2, which is a schematic diagram showing
the first embodiment of the audio control device 4 in accordance
with the present invention. The primary concept of this embodiment
is to apply a power selecting circuit 5 which can output a working
power selected from the primary power source 5 VAudio and the
auxiliary power source 5 Vaux to the Audio Codec 6 for driving the
same internal control amplifier circuit 61. Therefore, the audio
control device 4 of the present invention only needs one set of
internal control amplifier circuit 61 (which is built-in the Audio
Codec 6) to both operate on normal power-on status and perform the
Power OFF CD function.
[0038] The audio control device 4, as which shown in FIG. 2,
comprises a power selecting circuit 5 and an audio compiler/control
circuit 6 (also referred as Audio Codec hereinafter). The power
selecting circuit 5 receives the primary power source 5 VAudio
(also referred as the first power source hereinafter), a pry
control signal 3.3 Vdigital and an auxiliary power source 5 Vaux
(also referred as the second power source hereinafter). In this
embodiment, the power selecting circuit 5 comprises a separation
circuit 50 and a switch circuit 51. The separation circuit 50
comprises at least two Schottky diodes 501, 502 connected to each
other in parallel. The anode of the Schottky diode 500 is connected
to the primary power source 5 VAudio, while the anode of the other
Schottky diode 502 is connected to an output end of the switch
circuit 51. The joint output end (cathode) of these two Schottky
diodes 501, 502 is then further connected to the Audio Codec 6. By
employing these Schottky diodes 501, 502, the separation circuit 50
separates the primary power source 5 VAudio from the auxiliary
power source 5 Vaux. The switch circuit 51 comprises at least one
metal-oxide-semiconductor field effect transistor 510 (MOSFET)
having an input end thereof connected to the auxiliary power source
5 Vaux and a gate end thereof connected to the primary control
signal 3.3 Vdigital. The primary control signal 3.3 Vdigital acts
as a selecting signal of the switch circuit 51 in a manner that,
when the primary control signal 3.3 Vdigital is at a high level
status (i.e., when the PC is power-on), the switch circuit 51 will
be switched OFF such that the 5 Vaux will not be output by the
switch circuit 51. On the other hand, when the 3.3 Vdigital is at a
low level status (i.e., when the PC is power-off), the switch
circuit 51 will be switched ON so as to output the 5 Vaux to the
Audio Codec 6. That is, the switch circuit 51 can control the
output of the 5 Vaux in such a manner that the auxiliary power
source 5 Vaux is output only if the PC is at the power-off status.
On the other hand, when the PC is power-on, the primary power
source 5 VAudio can be provided to the Audio Codec 6 through the
separation circuit 50 such that the Audio Codec 6 can operate under
normal PC power-on condition.
[0039] It is notable that, although the switch circuit 51
illustrated in FIG. 2 uses the primary control signal 3.3 Vdigital
as the selecting signal to decide whether or not to output the
auxiliary power source 5 Vaux. However, any person who is skilled
in the art will be very easy to modify the switch circuit so as to
use the primary power source 5 VAudio to act as the selecting
signal of the switch circuit.
[0040] The Audio Codec 6 (audio compiler/control circuit) is a
single IC chip and generally comprises an audio compiler circuit
60: and a control amplifier circuit 61 built therein. The Audio
Codec 6 is connected to the ports of CD_L, CD_R and CD_GND of a
CD-ROM device for receiving audio signals therefrom. Theses audio
signals are processed and amplified by the audio compiler circuit
60 and a control amplifier circuit 61 and then output to the
speakers 40, 41 via the ports of Out_L and Out_R. The Audio Codec 6
further connects to the 3.3 Vdigital for control signal of digital
control logic thereof. In this preferred embodiment, there are two
outputs from the power selecting circuit 5, wherein one of the
output is from the switch circuit 51 and is connected only to the
control amplifier circuit 61 of the Audio Codec 6, while the other
output is from the primary power source 5 Vaudio and is connected
to both the audio compiler circuit 60 and the control amplifier
circuit 61. However, in another embodiment, the output of the power
selecting circuit 5 can also be a joint single output which is
directly connected to the control amplifier circuit 61.
[0041] The audio compiler circuit 60 of the Audio Codec 6 is driven
by both the primary power source 5 VAudio and the primary control
signal 3.3 Vdigital and is active only when the PC is power-on. The
audio compiler circuit 60 is for performing the analog/digital
signal transformations. That is, the audio signals can be converted
into digital signals by the audio compiler circuit 60 for further
operation handled by PC, for example, to be converted into a
digital file, to be processed by software, or be saved in a Hard
Disk of PC. On the other hand, digital signals accessed from the PC
or coming from the IDE cable (not shown in figures) of the CD-ROM
can be converted into audio signals by the audio compiler circuit
60 and then output through the speakers 40, 41. Since this audio
compiler circuit 60 is the same with the conventional technique and
forms little part of the present invention, therefore no more
description will be provided. The control amplifier circuit 61
accepts the input audio signals from the ports of CD_L, CD_R and
CD_GND of the CD_ROM device and outputs amplified output signals to
the speakers 40, 41 through the output ports of Out_L and Out_R.
Because the control amplifier circuit 61 of the Audio Codec 6 is
connected to the power selecting circuit 5, therefore it can
operate even when the PC is power-off, that is, to provide
so-called "Power OFF CD" function.
[0042] As shown in the enlarged circuit block of FIG. 2, a
preferred embodiment of the control amplifier circuit 61 comprises
a first amplifier circuit 610, a second amplifier circuit 611, a
third amplifier circuit 612, a fourth amplifier circuit 613, a
first channel switch 614, a second channel switch 616, a first mute
switch 615, and a second mute switch 617. The first amplifier
circuit 610 is connected to the second amplifier circuit 611 in
serial so as to process a first channel (e.g. the left channel
CD_L) of the audio signal. And, the third amplifier circuit 612 is
connected to the fourth amplifier circuit 613 in serial so as to
process a second channel (e.g. the right channel CD_R) of the audio
signal. The first and the third amplifier circuits 610, 612 each
has an input end thereof connecting to the ground signal port
"CD_GND" of the CD-ROM device for receiving the ground signal as a
reference to eliminate the Noise generated by the CD-ROM device. As
a result, a better effect of audio output can be obtained. In this
embodiment, the mute switches 615, 617 are normally "ON" when the
PC is power-off. However, when the PC is power-on, the mute
switches 615,617 are controllable by the computer software. Such
that the PC will be able to control whether or not to output audio
signals through the control amplifier circuit 61 by using computer
software when the PC is power-on.
[0043] Please refer to FIG. 3, which is a schematic diagram
illustrating the second preferred embodiment of the audio control
device 8 in accordance with the present invention. In this
preferred embodiment, most elements are similar to which previously
illustrated in FIG. 2, thus only schematic block diagram is
provided herewith. The most significant difference between the
audio control device 8 shown in FIG. 3 and the other audio control
device 4 illustrated in FIG. 2 is that the power selecting circuit
7 and the audio compiler/control circuit 9 are now integrated into
a single IC chip (e.g. the Audio Codec chip). Since the audio
control device 8 and the power selecting circuit 7 could be the
same as which disclosed in FIG. 2, therefore no detailed
description to these two elements are provided here.
[0044] Please refer to FIG. 4, which is a schematic diagram showing
a status table of power selection performed by the power selecting
circuit 7 of FIG. 3. As shown in FIG. 4, the primary power source 5
VAudio is connected in parallel with the ground through a
resistance 70 before being output as a power source, and auxiliary
power source 5 Vaux is also connected in parallel with the ground
through another resistance 71 before being output as a power
source. The primary power source 5 VAudio connects to the gate of
the MOS transistor 73, and the auxiliary power source 5 Vaux
connects to the drain (input end) of the MOS transistor 73 through
a resistance 72. The source (output end) of the MOS transistor 73
is connected to the ground. A VC signal (voltage control signal) is
extracted from the drain of the MOS transistor 73. The state of VC
can be used to detect whether the auxiliary power supply is
available or not. The status of VC of the MOS transistor 73 can be
presented by the status table shown in FIG. 4.
[0045] As shown in the status table shown in FIG. 4, when the 5
Vaux and the 5 VAudio are both at logic low (0), it shows that no
power is supplied by the primary power supply and auxiliary power
supply, so the state of the power supply is OFF and the VC is at
logic low (0). When the 5 VAudio is at logic low (0) but the 5 Vaux
is at logic high (1), it shows that the auxiliary power source 5
Vaux is available but the primary power source 5 VAudio is off, and
therefore the VC is at logic high (1). When the 5 VAudio is at
logic high (1), it shows that the state of the primary power supply
is in a NORMAL operation state (PC power ON), that is, the CD-ROM
is using the primary power source 5 VAudio of the computer and thus
the VC signal is at logic low (0).
[0046] FIG. 5 is a schematic diagram showing the power selecting
circuit being applied to an amplifier of the internal amplifier
circuit of the present invention so as to obtain the same status
table as which illustrated in FIG. 4. The amplifier 700 shown in
FIG. 5 can be applied to some of the amplifier circuits
610.about.613 of the control amplifier circuit 61 illustrated in
FIG. 2 to achieve the same status table as which illustrated in
FIG. 4. The MOSFETs 74, 75 are connected to the power input end of
the amplifier 700 so as to control which one of the power sources
(either 5 VAudio or 5 Vaux) is to be supplied to the amplifier 700.
This is achieved by using the VC and the 5 VAudio as the control
signal to control the gates of the MOSFET 74 and the MOSFET 75
respectively.
[0047] FIG. 6 is a schematic diagram showing a more detail of the
internal amplifier circuit in accordance with the present
invention. The internal amplifier circuit comprises a volume
control circuit 80 shown in FIG 6. It is noted that, the internal
amplifier circuit of FIG. 6 can also be considered as a detailed
enlarged view of some part of the control amplifier circuit 61
shown in FIG. 2. In which, the amplifier 701 can be accordance with
the first amplifier circuit 610 (or the third amplifier circuit
612), the amplifier 702 can be accordance with the second amplifier
circuit 611 (or the fourth amplifier circuit 614), and the
combination of the switches 76, 77 can be accordance with the first
channel switch 614 (or the second channel switch 616). As shown in
FIG. 6, the output route of the audio signal CD-L (or CD-R) is
controlled by the switches 76, 77 and will change depending on
which power source (either 5 VAudio or 5 Vaux) is supplied thereto.
If the control amplifier circuit 61 is using the auxiliary power
source 5 Vaux (also referred as the first control status), the
audio signal CD-L (or CD-R) output from the amplifier 701 will go
through the resistance 78 and the MOSFET 76 (which is controlled by
VC), and then be amplified by the amplifier 702 before being output
to the Out_L (or Out_R) speaker. When the control amplifier circuit
61 is driven by the primary power source 5 Vaudio (also referred as
the second control status), then the audio signal CD-L (or CD-R)
output from the amplifier 701 will go through the volume control
circuit 80, the resistance 79 and the MOSFET 77 (which is
controlled by 5 VAudio), and then be amplified by the amplifier 702
before being output to the Out_L (or Out_R) speaker. It can be seen
that the volume control circuit 80 is only activated when the
primary power sources (5 VAudio and 3Vdigital) are available. The
volume control circuit 80 can be controlled by computer software
such that users will be able to adjust the volume of the sounds by
using the computer software. Therefore, no matter the PC is
power-on or power-off, the internal amplifier circuits of the Audio
Code chip can always be driven by the selected power output from
the power selecting circuit. Moreover, because the signal
transmitting routes for different power sources (5 VAudio or 5
Vaux) are different and do not interfere each other, the same
control amplifier circuit 61 can be used in two power supply
conditions. That is, the audio control device 4 (or the audio
control device 8) of the present invention will be able to employ
only one set of control amplifier circuit 61 to operate in both PC
power-on and PC power-off statuses. As a result, the number of
components, cost and space needed for the circuits are reduced.
[0048] It is notable that, the aforementioned embodiments of the
power selecting circuits 5, 7 shown in FIGS. 2, 3 are merely for
illustrating some of the examples for achieving the aforesaid
objects of the present invention only and should not be used to
limit the overall scope of the present invention. Any person who is
skilled in the art might perform minor modification to the power
selecting circuit to obtain the same result easily. The present
invention aims to apply a power selecting circuit as a power
management unit to cooperate with the Audio Codec in such a manner
that, no matter the PC is power-on or power-off, the internal
amplifier circuits of the Audio Code can always be driven by a
power output from the power selecting circuit selected from the
primary power source 5 VAudio and the auxiliary power source 5
Vaux. Therefore, any modifications made by following the same
concept to achieve similar results should be considered to be
obvious to the present invention.
[0049] While the present invention has been shown and described
with reference to a preferred embodiment thereof, and in terms of
the illustrative drawings, it should be not considered as limited
thereby. Various possible modification, omission, and alterations
could be conceived of by one skilled in the art to the form and the
content of any particular embodiment, without departing from the
scope and the spirit of the present invention.
* * * * *